Which Government said its voluntary?
International law as well as domestic certainly does say that.
The first article of the Treaty of Union reads:
"That the Two Kingdoms of Scotland and England, shall upon the 1st May next ensuing the date hereof, and forever after, be United into One Kingdom by the Name of Great Britain."
That applies to Northern Ireland as well. Exactly the same political reality as in every country in Europe, in fact!
The reason why the UK is a partnership of equals aka Union Of Equals is because every constituent citizen has one vote for one MP.
A citizen in London, Edinburgh, Cardiff and Belfast all have exactly one vote each which is the definition of equal.
If you're seriously suggesting that Scotland, Wales and Northern Ireland should have exactly the same voting power as a bloc as England, well that would definitely be inequal. That's because the 15% bloc would have the same power as the 85% bloc. Its logically unequal.
That's why 1:1 is the definition of equal and why citizens in every part of the UK has the same number of votes to cast however they see fit. And this is very important because the UK is a UNITARY SOVEREIGN STATE! You, on the other hand, are talking as though each part of the UK is completely separate from each other. That's clearly false.
We have the same rights, same opportunities, same consular protection and, by and large, the same laws as each other. We even have the same Monarch. That's equal.
The equals in the union are the people and NOT the constituent parts we call England, Scotland, Wales and Northern Ireland. Each person in the U.K. has the same identical democratic power. No more, no less.
To claim anything else is to engage in distortion and aim to deliberately mislead the people.
We ARE a union of equals within a single UNITARY SOVEREIGN STATE known as the United Kingdom of Great Britain and Northern Ireland.
England, Scotland, Wales were all abolished as separate independent and sovereign countries.
And replaced with the United Kingdom of Great Britain. Northern Ireland came later.
Oh, and the UK does have a mechanism as seen in Scotland and Northern Ireland's Good Friday Agreement. The unitary sovereign state itself does NOT have to lay out the full criteria for secession either. This, too, is settled law....